Lining/fairing panel and method for measuring the electrical bonding resistance of a lining/fairing panel

ABSTRACT

A lining/fairing panel, in particular a lining/fairing panel for an airborne vehicle such as an aircraft or a spacecraft is provided. The lining/fairing panel includes a panel body having a first surface and a second surface opposite to the first surface, an electrically conductive coating applied to the first surface or the second surface, and a via arranged in the panel body reaching from the first surface to the second surface of the panel body. The via is formed in an inner region of the panel body. The borders of the inner region are spaced apart by a predetermined distance from the borders of the first and second surface of the panel body.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/725,054, filed Nov. 12, 2012, and to European Patent ApplicationNo. 12 192 226.4, filed Nov. 12, 2012, and is a continuation of U.S.patent application Ser. No. 14/066,772 filed Oct. 30, 2013, which areeach incorporated herein by reference in their entirety.

TECHNICAL FIELD

This application pertains to a lining/fairing panel and a method formeasuring the electrical bonding resistance of a lining/fairing panel,particularly to be used for an electromagnetic and lightning protectionlining/fairing of an aircraft or spacecraft.

BACKGROUND

Non-conductive panels for an airborne vehicle such as an aircraft or aspacecraft represent an electromagnetic aperture in the internal andexternal hull of the airborne vehicle. In order to protect an aircraftfrom the effects of lightning strikes and High Intensity ExternalRadiated Fields (HIRF), a conductive layer is usually applied to thesurface of such lining and fairing panels. The conductive layer iselectrically connected to adjacent conductive structural components ofthe airborne vehicle such as metallic fuselage or hull parts.

In order to check the proper functionality of the lining/fairing panelsafter installation, it is desirable to measure the electrical bondingresistance between a lining/fairing panel with a conductive surfacecoating and the respective conductive structural components of theairborne vehicle to which the lining/fairing panel is attached. Theelectrical bonding resistance is an important parameter to ensureelectromagnetic compatibility (EMC) and lightning protection capabilityof the lining/fairing of an airborne vehicle.

U.S. Pat. No. 4,755,904 A discloses a composite material skin attachedto a composite material structure using metal lock bolts. A foraminousmetal layer is arranged on the composite material skin to divert currentgenerated by lightning strikes away from the metal lock bolts.

European Patent No. 2 402 248 A2 discloses aircraft panels made ofcomposite materials having a metallization structure thereon and metalfixing elements stuck through bores in the aircraft panels for bondingthe aircraft panels to structural aircraft elements.

In addition, other objects, desirable features and characteristics willbecome apparent from the subsequent summary and detailed description,and the appended claims, taken in conjunction with the accompanyingdrawings and this background.

SUMMARY

According to various embodiments, provided is a means to measure theelectrical bonding resistance for a lining/fairing panel of an airbornevehicle to the structural elements of the airborne vehicle of which maybe measured in readily accessible and uncomplicated manner.

According to a one of various aspects of the present disclosure, alining/fairing panel, in particular a lining/fairing panel for anairborne vehicle such as an aircraft or a spacecraft, comprises a panelbody having a first surface and a second surface opposite to the firstsurface, an electrically conductive coating applied to the first surfaceor the second surface, and a via arranged in the panel body reachingfrom the first surface to the second surface of the panel body, the viabeing formed in an inner region of the panel body the borders of whichinner region are spaced apart by a predetermined distance from theborders of the first and second surface of the panel body.

According to another of various aspects of the present disclosure, anairborne vehicle comprises a plurality of lining/fairing panelsaccording to various embodiments mounted on structural elements of theairborne vehicle.

According to one of various aspects of the present disclosure, a methodfor measuring the electrical bonding resistance of a lining/fairingpanel according to various embodiments to a structural element of anairborne vehicle such as an aircraft or a spacecraft comprises forcingan electrical current through the bolt, the electrically conductivecoating and the structural element, measuring a voltage drop between thebolt and the structural element, and determining the electrical bondingresistance of a lining/fairing panel dependent on the measured voltagedrop.

One main idea of the present disclosure is to provide for alining/fairing panel for use in an airborne vehicle which is part of anelectromagnetic interference (EMI) and lightning protection system. Thenecessary electrically conductive bonding to the structural elements ofthe airborne vehicle on which the lining/fairing panel is mounted may bemeasured with the aid of an electrically conductive bolt arranged in avia reaching through the panel body of the lining/fairing panel. Thebolt is electrically coupled to an electrically conductive coatingapplied to a surface of the panel body.

One advantage of such a lining/fairing panel is the ease ofaccessibility for measuring the electrical bonding resistance to theunderlying structural element such as a fuselage or hull component.Irrespective of whether the electrically conductive coating faces thestructural element, the bolt is always accessible from the outside, forexample for resistance measurements.

Particularly advantageous is the fact that the electrically conductivecoating will not have to be damaged or altered when measuring theelectrical bonding resistance. This facilitates a measurement when thelining/fairing panel has already been applied in its final mountingplace.

Finally, the electrical bonding resistance measurements may be performedeasily in the component production phase, for example during acceptancetest procedures, in the aircraft manufacturing phase after theinstallation of the lining/fairing panels, in a maintenance, repair andoverhaul (MRO) phase or in a troubleshooting phase. This is particularlyuseful since the lining/fairing panels do neither need to bede-installed nor damaged for these kind of measurements.

The lining/fairing panel is thus always electrically accessible fromboth sides of the panel body.

According to an exemplary embodiment of the lining/fairing panel, thelining/fairing panel may comprise a bolt comprising an electricallyconductive material arranged in the via, the bolt being electricallycoupled to the electrically conductive coating.

According to another exemplary embodiment of the lining/fairing panel,the lining/fairing panel may further comprise a nut arranged on thesecond surface of the panel body, wherein the bolt is a threaded boltthreadingly engaging the nut.

According to one exemplary embodiment of the lining/fairing panel, thelining/fairing panel may further comprise a first washer comprising anelectrically conductive material, the first washer being arrangedbetween the nut and the second surface of the panel body.

According to another exemplary embodiment of the lining/fairing panel,the electrically conductive coating may be applied to the second surfaceof the panel body, and the first washer may extend over at least part ofthe electrically conductive coating electrically coupling theelectrically conductive coating to the bolt.

According to one embodiment of the lining/fairing panel, thelining/fairing panel may further comprise a second washer comprising anelectrically conductive material, the second washer being arrangedbetween the bolt head and the first surface of the panel body.

According to another exemplary embodiment of the lining/fairing panel,the electrically conductive coating may be applied to the first surfaceof the panel body, and the second washer may extend over at least partof the electrically conductive coating electrically coupling theelectrically conductive coating to the bolt.

According to one embodiment of the lining/fairing panel, the secondwasher may have a conical shape, and the via may comprise a conicallyshaped opening broadening towards the first surface configured toreceive the second washer within the opening.

According to an exemplary embodiment of the lining/fairing panel, thepanel body may comprise a monolithic and electrically non-conductiveglass fibre composite material.

According to various embodiments of the lining/fairing panel, the panelbody may comprise at least two layers of glass fibre composite materialsandwiching a honeycomb core structure.

According to one exemplary embodiment of the lining/fairing panel, afiller of conductive or non-conductive material may be arranged in thesandwich panel body surrounding the via.

According to another embodiment of the lining/fairing panel, thelining/fairing panel may further comprise a surface protection layerapplied to the electrically conductive coating.

A person skilled in the art can gather other characteristics andadvantages of the disclosure from the following description of exemplaryembodiments that refers to the attached drawings, wherein the describedexemplary embodiments should not be interpreted in a restrictive sense.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will hereinafter be described in conjunctionwith the following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 shows a lining/fairing panel for an airborne vehicle according tovarious embodiments of the present disclosure.

FIG. 2 shows a lining/fairing panel in greater detail according toanother one of various embodiments of the present disclosure.

FIG. 3 shows a lining/fairing panel in greater detail according toanother exemplary embodiment of the present disclosure.

FIG. 4 shows a lining/fairing panel in greater detail according toanother exemplary embodiment of the present disclosure.

FIG. 5 shows a lining/fairing panel in greater detail according toanother exemplary embodiment of the present disclosure.

FIG. 6 shows a method for measuring the electrical bonding resistance ofa lining/fairing panel according to various embodiments.

FIG. 7 shows an airborne vehicle having two lining/fairing panelsaccording to various embodiments.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the present disclosure or the application and usesof the present disclosure. Furthermore, there is no intention to bebound by any theory presented in the preceding background or thefollowing detailed description.

FIG. 1 shows a lining/fairing panel 10, particularly a lining/fairingpanel 10 for use in an airborne vehicle such as an aircraft orspacecraft. One or more lining/fairing panels 10 may be used in anaircraft such as the aircraft 100 as shown exemplarily in FIG. 7. Theaircraft 100 of FIG. 7 may comprise one or more lining/fairing panels 10mounted to structural elements of the aircraft 100 such as fuselage orhull components. FIG. 1 shows two views of a lining/fairing panel 10—(a)is a view on one surface of the lining/fairing panel 10, whereas (b) isa view from the other side of the lining/fairing panel 10.

The lining/fairing panel 10 may comprise a panel body 1 which may besubstantially oblong or rectangular in shape. Of course, othergeometrical shapes and dimension of the lining/fairing panel body 1 maybe possible as well. The lining/fairing panel 10 may substantially beflat or slightly curved depending on the area of the hull of an airbornevehicle where the lining/fairing panel 10 is intended to be mounted.

The panel body 1 may have a lower surface 5 and an upper surfaceopposite to the lower surface 5. The upper surface—in the case of FIG. 1the top side of (b)—may be coated with an electrically conductivecoating. The panel body 1 may comprise a generally electricallynon-conductive material, for example glass fibre composite material orlayered glass fibre composite material having a honeycomb coresandwiched between. Alternatively, the panel body 1 may comprise acarbon fibre resin plastic (CFRP) material.

The electrically conductive coating 6 may be applied to all or only partof the upper surface of the panel body and may for example comprisemetal meshes, metal foils, sprayed metal, woven wire fabrics, metallizedfiberglass, antistatic coatings, metal loaded paints or vapour depositedmetal layers, made from, for example, copper, bronze, aluminium, nickelor silver. It may also be possible to use polyurethane or epoxy matriceshaving metallic nanoparticles made from silver, nickel, aluminium,bronze or copper dispersed therein. The electrically conductive coating6 may additionally be coated with a surface protection layer (notshown), for example enamel, varnish or paint.

The panel body 1 may be fastened to the structural elements of anairborne vehicle by means of fasteners 2 arranged at the borders of thepanel body 1. The number and type of fasteners may be chosen accordingto the needs of the area of application, bearing in mind to avoidcorrosion of the fasteners and the electrically conductive coating 6 asmuch as possible. The panel body 1 may have an inner region 4 which isspaced apart from the borders of the panel body 1 by a predetermineddistance. Within the inner region 4 one or more vias 3 may be arrangedreaching the lower surface 5 to the upper surface and through theelectrically conductive coating 6.

The via 3 may for example be a round through-hole, although other shapesmay be possible for the via 3 as well. The via 3 may comprise a via axisA substantially oriented in parallel to a normal vector of the planedefined by the panel body 1.

As will be shown with respect to FIGS. 2 to 5, the via 3 is configuredto receive a bolt 11 within the opening defined by the via 3.

FIGS. 3 and 5 refer to the situation where the electrically conductivecoating 6 is applied on one of the surfaces of the panel body 1, inparticular the surface adjacent to the bolt head of the bolt 11. On thecontrary, FIGS. 2 and 4 refer to the situation where the electricallyconductive coating 6 is applied on the opposite surface opposite to thebolt head of the bolt 11.

In FIGS. 4 and 5, the panel body 1 comprises a monolithic andelectrically non-conductive glass fibre composite material. In FIGS. 2and 3, the panel body 1 comprises a layered glass fibre compositematerial sandwiching a honeycomb core. For the FIGS. 2 and 3, in thesurrounding of the via 3, filler material 15 may be arranged tomechanically stabilize the via 3.

Referring to the common features of FIGS. 2 to 5, a bolt 11 is arrangedwithin the opening defined by the via 3. The bolt 11 may be a threadedbolt 11, which threadingly engages a nut 14 on the opposite side of thepanel body 1. The bolt 11 may comprise an electrically conductivematerial such as aluminium, titanium, titanium alloy or stainless steel.The material of the bolt 11 may be chosen optimized for anti-corrosionproperties.

Between the nut and the lower surface of the panel body 1, a firstwasher 13 may be arranged. The first washer 13 may be a flat washer.Between the bolt head of the bolt 11 and the upper surface of the panelbody 1 a corresponding second washer 12 or 16 may be arranged. Dependingon which surface of the panel body 1 the electrically conductive coating6 is applied, the respective washer 12, 13 or 16 may have a washer rimextending over at least part of the electrically conductive coating 6 toelectrically couple the coating 6 to the bolt 11.

In FIGS. 3 and 5, the second washer 16 may have a conical shape and thevia 3 may define an opening having a conical shape widening towards theupper surface, the opening being configured to receive the second washer16 therein. To that end, the edges of the filler material 15 may beslanted, bevelled or tapered correspondingly. The bolt 11 may in thesecases be a counter sunk bolt or a counter sunk screw.

In FIGS. 2 and 4, the bolt 11 may in particular be a bolt having arounded head such as a fillister head screw or a button head screw. Inthese cases the second washer 12 may be a flat washer frictionallyengaged to the flat surface of the panel body 1.

Of course, the bolt and washer solution of FIGS. 2 and 4 may as well beemployed in the embodiments of FIGS. 3 and 5 where the electricallyconductive coating 6 is arranged on the opposite side. Similarly, thebolt and washer solution of FIGS. 3 and 5 may be employed in theembodiments of FIGS. 2 and 4.

The lining/fairing panel 10 as shown in FIGS. 1 to 5 may be mounted onor in an aircraft with the electrically conductive coating 6 facing thestructural elements of the aircraft or with the electrically conductivecoating 6 facing outside. Irrespective of what installation geometry ischosen, the bolt 11 is always accessible from outside to performelectrical bonding resistance measurements at the lining/fairing panel10.

FIG. 6 schematically illustrates a method 20 for measuring theelectrical bonding resistance of a lining/fairing panel such as thelining/fairing panel 10 as exemplarily explained in conjunction withFIGS. 1 to 5 to a structural element of an airborne vehicle. The method20 may for example be employed for measurements of lining/fairing panels10 installed on or in an aircraft such as the aircraft as exemplarilyshown in FIG. 7. The method 20 may for example be used in the componentproduction phase, for example during acceptance test procedures, in theaircraft manufacturing phase after the installation of thelining/fairing panels, in a maintenance, repair and overhaul (MRO) phaseor in a troubleshooting phase.

At 21, an electrical current is forced through the bolt, theelectrically conductive coating and the structural element. Then, at 22,a voltage drop between the bolt and the structural element is measured.Dependent on the measured voltage drop, the electrical bondingresistance of the lining/fairing panel 10 may be determined at 23. Themethod 20 may for example be implemented using a four point probe methodor a two point probe method, wherein the resistance of the electricallyconductive coating is dependent on a current flowing throughout thecoating and a voltage drop between the coating and the structuralelement to which the lining/fairing panel is mounted.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of thepresent disclosure in any way. Rather, the foregoing detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment, it being understood thatvarious changes may be made in the function and arrangement of elementsdescribed in an exemplary embodiment without departing from the scope ofthe present disclosure as set forth in the appended claims and theirlegal equivalents.

What is claimed is:
 1. A method for measuring the electrical bondingresistance of a lining/fairing panel mounted on a structural element ofan airborne vehicle, the lining/fairing panel comprising: a panel bodyhaving a first surface and a second surface opposite to the firstsurface; an electrically conductive coating applied to the first surfaceor the second surface; and a via arranged in the panel body reachingfrom the first surface to the second surface of the panel body, the viabeing formed in an inner region of the panel body the borders of whichinner region are spaced apart by a predetermined distance from theborders of the first and second surface of the panel body, the methodcomprising the steps of: forcing an electrical current through the bolt,the electrically conductive coating and the structural element;measuring a voltage drop between the bolt and the structural element;and determining the electrical bonding resistance of a lining/fairingpanel dependent on the measured voltage drop.
 2. The method of claim 1,wherein the lining/fairing panel further comprises a bolt comprising anelectrically conductive material arranged in the via, the bolt beingelectrically coupled to the electrically conductive coating.
 3. Themethod of claim 2, wherein the lining/fairing panel further comprises anut arranged on the second surface of the panel body, wherein the boltis a threaded bolt threadingly engaging the nut.
 4. The method of claim3, wherein the lining/fairing panel further comprises a first washercomprising an electrically conductive material, the first washer beingarranged between the nut and the second surface of the panel body. 5.The method of claim 1, wherein the electrically conductive coating isapplied to the second surface of the panel body, and wherein the firstwasher extends over at least part of the electrically conductive coatingelectrically coupling the electrically conductive coating to the bolt.6. The method of claim 1, wherein the lining/fairing panel furthercomprises a second washer comprising an electrically conductivematerial, the second washer being arranged between the bolt head and thefirst surface of the panel body.
 7. The method of claim 6, wherein theelectrically conductive coating is applied to the first surface of thepanel body, and wherein the second washer extends over at least part ofthe electrically conductive coating electrically coupling theelectrically conductive coating to the bolt.
 8. The method of claim 7,wherein the second washer has a conical shape, and wherein the viacomprises a conically shaped opening broadening towards the firstsurface configured to receive the second washer within the opening. 9.The method of claim 1, wherein the panel body comprises a monolithic andelectrically non-conductive glass fibre composite material.
 10. Themethod of claim 1, wherein the panel body comprises at least two layersof glass fibre composite material sandwiching a honeycomb corestructure.
 11. The method of claim 10, wherein a filler of conductive ornon-conductive material is arranged in the panel body surrounding thevia.
 12. The method of claim 1, wherein the lining/fairing panel furthercomprises a surface protection layer applied to the electricallyconductive coating.